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Miscellaneous Serverless

AWS Step Functions​

  • Model your workflows as state machines (one per workflow)
    • Order fulfillment, Data processing
    • Web applications, Any workflow
  • Written in JSON
  • Visualization of the workflow and the execution of the workflow, as well as history
  • Start workflow with SDK call, API Gateway, Event Bridge (CloudWatch Event)

Task States​

  • Do some work in your state machine
  • Invoke one AWS service
    • Can invoke a Lambda function
    • Run an AWS Batch job
    • Run an ECS task and wait for it to complete
    • Insert an item from DynamoDB
    • Publish message to SNS, SQS
    • Launch another Step Function workflow…
  • Run an one Activity
    • EC2, Amazon ECS, on-premises
    • Activities poll the Step functions for work
    • Activities send results back to Step Functions

step-functions

States​

  • Choice State - Test for a condition to send to a branch (or default branch)
  • Fail or Succeed State - Stop execution with failure or success
  • Pass State - Simply pass its input to its output or inject some fixed data, without performing work.
  • Wait State - Provide a delay for a certain amount of time or until a specified time/date.
  • Map State - Dynamically iterate steps.’
  • Parallel State - Begin parallel branches of execution.

Visual workflow​

step-functions-workflow

Error Handling​

  • Any state can encounter runtime errors for various reasons:
    • State machine definition issues (for example, no matching rule in a Choice state)
    • Task failures (for example, an exception in a Lambda function)
    • Transient issues (for example, network partition events)
  • Use Retry (to retry failed state) and Catch (transition to failure path) in the State Machine to handle the errors instead of inside the Application Code
  • Predefined error codes:
    • States.ALL : matches any error name
    • States.Timeout: Task ran longer than TimeoutSeconds or no heartbeat received
    • States.TaskFailed: execution failure
    • States.Permissions: insufficient privileges to execute code
  • The state may report is own errors

Retry (Task or Parallel State)​

step-function-retry

  • Evaluated from top to bottom
  • ErrorEquals: match a specific kind of error
  • IntervalSeconds: initial delay before retrying
  • BackoffRate: multiple the delay after each retry
  • MaxAttempts: default to 3, set to 0 for never retried
  • When max attempts are reached, the Catch kicks in

Catch (Task or Parallel State)​

  • Evaluated from top to bottom
  • ErrorEquals: match a specific kind of error
  • Next: State to send to
  • ResultPath: A path that determines what input is sent to the state specified in the Next field

ResultPath​

step-function-result-path

Wait for Task Token​

  • Allows you to pause Step Functions during a Task until a Task Token is returned
  • Task might wait for other AWS ser vices, human approval, 3rd party integration, call legacy systems…
  • Append .waitForTaskToken to the Resource field to tell Step Functions to wait for the Task Token to be returned
  • Task will pause until it receives that Task Token back with a SendTaskSuccess or SendTaskFailure API call

waitForTaskToken

Activity Tasks​

  • Enables you to have the Task work performed by an Activity Worker
  • Activity Worker apps can be running on EC2, Lambda, mobile device…
  • Activity Worker poll for a Task using GetActivityTask API
  • After Activity Worker completes its work, it sends a response of its success/failure using SendTaskSuccess or SendTaskFailure
  • To keep the Task active:
    • Configure how long a task can wait by setting TimeoutSeconds
    • Periodically send a heartbeat from your Activity Worker using SendTaskHeartBeat within the time you set in HeartBeatSeconds
  • By configuring a long TimeoutSeconds and actively sending a heartbeat, Activity Task can wait up to 1 year

activity-tasks

Standard vs. Express​

step-function-standard-express

AWS AppSync​

  • AppSync is a managed service that uses GraphQL
  • GraphQL makes it easy for applications to get exactly the data they need.
  • This includes combining data from one or more sources
    • NoSQL data stores, Relational databases, HTTP APIs…
    • Integrates with DynamoDB, Aurora, OpenSearch & others
    • Custom sources with AWS Lambda
  • Retrieve data in real-time with WebSocket or MQTT on WebSocket
  • For mobile apps: local data access & data synchronization
  • It all starts with uploading one GraphQL schema

GraphQL Example​

graphql-example

AppSync Diagram​

appsync-diagram

Security​

  • There are four ways you can authorize applications to interact with your AWS AppSync GraphQL API:
  • API_KEY
  • AWS_IAM: IAM users / roles / cross-account access
  • OPENID_CONNECT: OpenID Connect provider / JSON Web Token
  • AMAZON_COGNITO_USER_POOLS
  • For custom domain & HTTPS, use CloudFront in front of AppSync

AWS Amplify​

  • Set of tools to get started with creating mobile and web applications
    • “Elastic Beanstalk for mobile and web applications”
    • Must-have features such as data storage, authentication, storage, and machine-learning, all powered by AWS services
    • Front-end libraries with ready-to-use components for React.js, Vue, Javascript, iOS, Android, Flutter, etc…
    • Incorporates AWS best practices to for reliability, security, scalability
  • Amplify Studio: Visually build full-stack app, FE and BE
  • Amplify CLI: Configure an Amplify backend with a guided CLI workflow
  • Amplify Libraries: Connect your app to existing AWS services (Cognito, S3 and more)
  • Amplify Hosting: Host apps or websites via the AWS content deliver network

Important Features​

amplify-important-features

Amplify Hosting​

  • Build and Host Modern Web Apps
  • CICD (build, test, deploy)
  • Pull Request Previews
  • Custom Domains
  • Monitoring
  • Redirect and Custom Headers
  • Password protection

End-to-End (E2E) Testing​

amplify-e2e